Reliability and validity of the Japanese version of the Pediatric Quality of Life Inventory Infant Scales

Background: PedsQL Infant Scales (PedsQL-I) are used to assess parent-reported health-related quality of life for children younger than 2 years. We determined the feasibility, reliability, and validity of the Japanese version of the PedsQL-I. Methods: A total of 183 participants (parents) with infants aged 1-30 months were recruited from 8 day care centers and one pediatric clinic. Participants completed the PedsQL-I (infants aged 1-18 months), the PedsQL-I and the PedsQL-Toddler version (infants aged 19-30 months), and the Kessler-6 psychological distress scale (all participants). We determined feasibility, internal consistency, test-retest reliability, concurrent validity, convergent and discriminant validity, known-groups validity with regard to acute and chronic illness, and relative and transitional validity with PedsQL-Toddler for the use in infants aged 25-30 months. Results: All subscales were internally consistent (Cronbach's alpha for 1-12 months: 0.88-0.98 and for 13-24 months: 0.85-0.97); test-retest reliability was acceptable (intra-class correlation coefficients > 0.40); and all scales were concurrently valid with the PedsQL-Toddler version (Pearson's product-moment correlation coefficient for the total score = 0.74). The scales' convergent and discriminant validity were acceptable (scaling success rate > 80%). Validation for known-groups showed that the Physical Health Summary score was sensitive to acute and chronic disease, the Psychosocial Health Summary score was sensitive to neither acute nor chronic disease, and the total score was sensitive to acute disease. Relative validity showed a ratio of 1.74 for the squared t values for the total score. Conclusions: The PedsQL-I is suitable for assessing health-related quality of life in infants aged 1-24 months in prospective studies.